|
| | CODE OF GOOD AGRICULTURE PRACTICE -
LITHUANIA
8. LAND RECLAMATION, BIOLOGICAL DIVERSITY AND
LANDSCAPE
8.1. REGULATION OF WATER REGIME
When drainage or irrigation is applied, natural
water circulation is disturbed and this certainly affects concentration of
biogenic materials in water. Surplus of biogenic materials (compounds of
nitrogen and phosphorus) in surface waters and in sources of drinking water is
harmful for aquatic fauna and human health. Therefore, during regulation of
water regime it is very important to protect ground and surface water from
pollution. Pollution of drinking water by nitrates is especially dangerous.
The dominant drainage type of fields in Lithuania is tile drainage, and ditches
are used for this purpose only in small amount. Land reclamation works were
carried out in complex installing not only tile drainage or open drainage
network but also many small hydrotechnical constructions that ensure reliable
operation of drainage systems.
When reclamation equipment gets out of order, they need reconstruction. This is
very expensive measure compared to annual expenditure for exploitation, so land
users have to know that maintenance of drainage systems is very important.
Right usage of watering installations is also very important as they can be of
benefit only then. If they are explored improperly they are not only
unprofitable but they can damage soil and pollute surface waters.
Problems of drinking water are very urgent in the countryside as water is
usually taken from drilled wells; therefore, adequate installation of sources of
drinking water, their maintenance and protection from pollution are very
significant. If we drink only pure water, we will not impair our children's and
our health.
8.1.1. Tile drainage and its maintenance
8.1
Landowner is responsible and he can not impede to ensure functioning of land
reclamation facilities in adjacent lands and also has not to violate the
rights of other users of water resources..
Every earthwork and construction of new buildings in drained areas must be co-ordinated
with State Land Reclamation Service.
Republic of Lithuania. Law on Land
Reclamation, 1993, V.
Republic of Lithuania. Law on Water,
1997, V.
Republic of Lithuania. Law on Land
Reclamation, 1993, V.
8.2
Landowner should be responsible for:
 | proper usage and maintenance of
drainage systems;
| quality of water flowing from the
drainage systems to adjacent territory;
| damage of the drainage systems and
pollution of water in the drainage systems. |
| |
In order to meet the above mentioned
requirements and to cultivate drained land it is recommended:
- Not to use fertilisers (organic and mineral)
and not to drive to fields with machinery when soil is so wet that machines
stick in, because then fertilisers percolate with water to deeper layers
quickly and get into drainage, and the sticking machines may break up
drainage tubes;
- To use household wastewater and liquid manure
for watering of drained land only after consulting a specialist;
- After the end of flood season it is needed:
| To check if drainage systems operate
sufficiently well and if all the area is evenly drained;
| To check if pits of funnel or other form and
gullies have not appeared in the area (this is a sign of ground suction in
the places of drainage damage or result of water erosion because of
obstruction of drainage pipes);
| If surface runoff inlets operate well;
| If there are no water erosion signs;
| To perform established maintenance work. |
| | | |
If the mentioned damages are observed, they have
to be eliminated without delay. One drainage system drains land of some farmers
usually. If we take care only about ourselves, our neighbours will suffer.
8.1.2. Ditches and surface drainage
8.3
Coastal protective strips are established at surface water bodies.
For regulated rivulets and reclamation ditches, which have basin area smaller
than 10 km2,
width of the preservation strip is determined depending on local conditions:
When inclination of riverside is up to 5 degrees 1 m;
When inclination of riverside is 5-10 degrees not smaller than 2.5 m;
When inclination of riverside is more than 10 degrees not smaller than 5
m.
Regulations on formation and maintenance
of preservation zones for water bodies, LTSR MT 1982 12 06 resolution No. 335.
On coastal preservation strips it is
prohibited: to build buildings (except for hydrotechnical ones), lay roads, use
fertilisers, pesticides and other chemicals harmful to environment, cultivate
land, destroy turf, graze cattle, arrange recreation places, leave a car, make
up a fire, cut trees and bushes.
8.4
Landowner must:
 | maintain a ditch that goes through
his land in order to create conditions for draining of adjacent areas;1
| not violate requirements
of preservation strips and zones. |
|
Special conditions on forest and land
use. LRG 1992.05.12, Resolution No. 343. V.
 Fig.
8.1. Water level during vegetation season when ditch is maintained properly and
improperly
The ditch will fully perform its duty and will not harm nature if a landowner
carries out the following works:
| puts washed out or slipped slopes and gutters
for surface water inlet to the ditch in order in every spring and autumn;
| mows grass at slopes and protective strips in
time;
| does not let bushes grow on slopes of the
ditch;
| does not let livestock to the ditch and
avoids any other damage of the slopes;
| removes appeared obstructions from the ditch
bed (e.g. remnants of trees and bushes);
| if needed, cleans openings of hydrotechnical
constructions (bridges, gutters, top streams, etc.) and creates conditions
for free water flow. |
| | | | |
8.1.3. Irrigation
Sprinkler irrigation systems have become most
spread and established among other irrigation systems in Lithuania. Irrigation
systems are most common for vegetables and cultivated pastures. Irrigation is
very effective in dry summers but it may also cause harm if used improperly.
8.5
When sprinkler irrigation technique
is used, such watering intensity should be chosen that water would have time
to soak into soil and surface runoff would not be formed, which would induce
erosion and washout of nutrients and humus.
During exploitation of sprinkler irrigation system it is important to water out
such amount of water that will be absorbed by that soil layer where plant roots
are present. If we water too strong (too intensively) then soil will not have
time to absorb the water coming to the surface and bogs will be formed. If we
water too long then water will percolate deeper than roots and will leak to
drainage (we will have unnecessary water losses). Water flowing from higher
places to lower will take away nutrients and humus. All this may be avoided if
engineer hydrotechnician is called, project of detailed irrigation regime is
prepared, and the amount of water for irrigated crop per whole season and per
one watering period is determined. It is not recommended to water if surface
slope is more than 2 %.
Besides sprinkler irrigation there could be used surface irrigation by small
furrows and drop irrigation. The surface irrigation suits to row crops. Drop
irrigation is very promising. Its key point is that a small tube is brought to
each plant and the water amount needed for the plant drips from the tube. Such
irrigation system is usually used in kitchen gardens and gardens. If liquid
manure and household wastewater are planned to be used for watering, one has to
be especially careful and consult specialists necessarily.
8.1.4. Sources of drinking water
Drinking water means
fresh water, extracted from natural
sources or specially prepared that meets the standard for drinking water
established in the Republic of Lithuania.
Water extraction site means
an area where water is extracted for the purpose of supplying it to users. Sanitary
protective zone around the water extraction site (SPZ) denotes
the protected area surrounding the water extraction site, which is subject to
certain limitations imposed on the activities of land users.
8.6
Drilled and dug wells located in the territory of land user are sources of
drinking water and laws regulate their protection. Sanitary protective zones
and strips shall be designated around the water extraction sites and single
wells; economic activities shall be regulated or prohibited there.
Lithuanian Republic. Law on Water, 1997.
Special conditions of forest and land
use. LRG 1992 05 12, resolution No. 343
Order on design, installation,
preservation and liquidation of bore wells for water supply and thermal energy
use. LAND 4-99. V., 1999.
SPZ is divided into two strips: strip of strict
regime (from accidental pollution) and restriction-sanitary protective strip
that has a particular regime determined. Parameters of the strip of strict
regime are determined considering local relief, geological-hydrological and
sanitary conditions. In all cases the strip of strict regime has to be not
smaller than 5 m radius around the drilled well. When there are unfavourable
natural (lower relief, unprotected water horizon, etc.) and sanitary conditions,
radius of the strip of strict regime around the drilled well can be extended up
to 30 m when condensable water horizon is explored and up to 50 m when ground
water horizon is explored.
8.7
Territory of the strip of strict regime has to be fenced (in exceptional cases
it may stay without fence if owner of the drilled well ensures safety of the
strip and pump of the well), planted, kept clean and protected. In the strip
of strict regime it is prohibited to store oil products, chemical and organic
materials, use pesticides, perform intensive agriculture, build objects that
are not related to water supply, etc.
Order on design, installation,
preservation and liquidation of bore wells for water supply and thermal energy
use. LAND 4-99. V., 1999.
Parameters (dimensions and form) of the restriction-sanitary protective strip
depend on local relief, existing pollution sites and hydrogeological conditions
and they are determined approximately when the place of well is chosen (the
strip is different in every case). It is recommended to discuss selection of
place for dug well with an engineer hydrogeologist, and installation and
maintenance of the well in farmstead with executive of local hygiene centre.
8.8
Dug well should be established in such a way that surface water or snow would
not get into it, animals and any things would not fall into it accidentally.
In the same time the well should have a ventilation hole. To protect ground
water flowing to the well from pollution, 50 m upstream from the well should
not be any farm buildings, field toilets, slurry pits, manure piles, storages
of fertiliser, pesticides and oil products as well as greenhouses and
intensively fertilised kitchen gardens.
 Fig.
8.2. Properly and improperly selected place for well
Dug well may be polluted due to improper manure storage, because liquid manure
and water percolating through manure infiltrate deeper, get into the first
water-bearing layer that feeds the well. So manure heap located even rather far
from the well may pollute it. It is not advisable to build a greenhouse or
fertilise kitchen garden intensively close to the well. Management of household
wastes also influences purity of water in the wells. If wastes are poured out
anywhere, appropriate toilets are not installed, then we can not expect to have
pure water in the well.
8.9
Consumers, who are not connected to centralised water supply network, provide
drinking water themselves and take care about its quality. Concentration of
nitrate in drinking water can not exceed 50mg/l. If because of installation of
new bore well there could arise wastewater, the installation is allowed only
when water consumer guarantees wastewater management.
Drinking water. Quality requirements and
program care. HN 24:1998. V., 1998.
Order on design, installation,
preservation and liquidation of bore wells for water supply and thermal energy
use. LAND 4-99. V., 1999.
Artesian wells are rather expensive and less common than drilled wells. But if
an artesian well exists inside landowner's land, the well has to be fenced (area
of the sanitary protective strip of strict regime). Any economic activity is
prohibited in the fenced zone except for mowing of grass.
8.2. BIOLOGICAL DIVERSITY AND
LANDSCAPE
Biological diversity
is understood as the whole complex of all living organisms species in
terrestrial, surface water and other ecosystems, their habitats and also their
genetic diversity.
Biological diversity induces productivity of
natural systems, functional diversity of natural environment, maintains its
resistance, adaptation and ability to recover. Natural and half-natural
terrestrial ecosystems are forests, swamps and meadows, water ecosystems are
rivers and lakes, and sea ecosystems Curonian Lagoon and Baltic Sea.
Affected by humans, or anthropogenic ecosystems are agricultural and urban
ecosystems. Biological diversity and landscape are unequally vulnerable to human
economic activity. The most sensitive places are river valleys, the Lower
Nemunas, lake-land in eastern Lithuania and karst region. Distribution of
Lithuanian territory according to vulnerability to human economic activity is
given in Fig. 8.3.
 Fig.
8.3. Lithuanian most sensitive (2) and especially sensitive (1) territories
where disturbance of biodiversity is expected (according to Lithuanian
Environmental Protection Ministry)
Biological diversity and landscape are
interrelated. The foundation for this is a natural frame the whole complex
of forests, groves and hills' caravans.
The natural frame is made of upper
reaches of the big rivers, groups of lakes, large marshlands, shores of large
water bodies, Lithuanian karst region, large river valleys, lakes' caravans and
large forest areas.
Landscape it is a complex of relief,
climate, weather, water, soil flora, fauna and cultural clothing. It
is changing continuously: field is replaced by forest, buildings are built and
tore down again, roads are built, marshes drained and rivulets dammed up. There
are distinguished natural (not affected by human activity) and anthropogenic
(agricultural and urban) landscape.
Biological diversity and natural biological resources are negatively affected
by:
| Intensive forest cutting, destroy of groves
and bush groups, industrial forestry when few most productive tree species
are grown;
| Changes of ecological conditions after
draining of large areas;
| Changes of water temperature and migration
paths after damming up of rivulets (fish migration paths are cut in this
way, temperature water regime changes);
| Increased recreative intensity in nature
(people from cities and small towns spend more time in nature);
| Development of road network and
intensification of traffic;
| Intensive hunting of wild animals not
considering their natural development and lack of continuous control;
| Intensification of agriculture;
| Pollution of air, dusts, water pollution by
industrial and agricultural pollutants, pollution of soils of urban
environment and physical urban pollution (noise, electromagnetic and thermal
pollution). |
| | | | | | |
8.3. CONSERVATION OF BIOLOGICAL
DIVERSITY AND LANDSCAPE
As agricultural landscape with
insertions of natural components comprises more than 70 % of Lithuanian
territory, farmers can help a lot in conservation of biological diversity and
restoration of traditional landscape.
whole complex of living organisms
species, their habitats and genetic diversity have to be preserved.
8.10
When cultural landscape is being formed, geoecological balance of landscape
has to be accomplished, i.e. green areas of natural frame (nuclear) have not
to be infringed. It preserves structure of the landscape.
Republic of Lithuania. Law on Protected
Areas, 1993, V.
In agricultural fields there should be grown various crops leaving islands of
natural nature. It is advisable to use environmental friendly technologies for
soil tillage and to preserve diversity of field edges.
River valleys, the most sensitive places on lake coast are preserved following
requirements for water protective zones and eutrophication of waters is reduced
in the same time. Trees and bushes of various age have to be conserved in
groves, riverside bush-groups and they have to be enlarged preserving Natural
Frame.
Agricultural landscape it is cultivated lands with crop fields, dwelling
houses and farmstead buildings and vegetation surrounding them (Fig. 8.4).
 |
Fig. 8.4. Traditional Lithuanian
landscape |
It is recommended to plant more trees of local
varieties and bushes in farmsteads (Fig. 8.5).
| Fig. 8.5. Farmsteads surrounded by
natural vegetation protect from wind well and form good shelter
conditions for wild animals |
 |
It is useful to combine borders of crop rotation fields with existing relief,
trees, bush-groups, big stones and historical-cultural heritage.
Landscape in protected territories and natural structure in karst region
(Northern Lithuania) have to be conserved with help of reduction of human impact
and stimulation of ecological farming.
8.11
Meadows, groves, wetlands and ponds should be located in the landscape
according to documents of territorial planning.
Outskirts of drained fields, meadows, pastures and forests, existing stone heaps
and hedges have not their numerous flora and fauna they have to be preserved
and augmented.
Single trees with hollows and nests, anthills should be preserved by augmenting
and fencing them in.
8.12
It is prohibited to destroy and infringe protected kinds of fauna, fungies and
its communities as well as habitats and residence.
Republic of Lithuania. Law on Protected
Animal, Plant and Fungi Species and Communities, 1997.
Introduced varieties of trees and bushes should not be expanded in settlements
and estates that have cultural residual value. On farm it is recommended to keep
local plant varieties giving preference only to varieties that are registered
for region and acknowledged.
8.13
Landowners and users are obliged to preserve natural and cultural heritage
objects.
Republic of Lithuania. Law on Protected
Areas, 1993, V.
Natural heritage objects are geological (unique pebbles, rocks and sinkholes),
hydrogeological (springs with special properties), geomorphological (hills,
ravines and gullies), hydrographic (impressive shoals, old riverbeds and
waterfalls), botanical and zoological.
Cultural heritage objects are archaeological (ancient mounds, defensive
fortifications, ancient production sites, sacral mythological stones and
places), memorial (closed cemetery), architectural-church, farm and industrial
buildings and engineering buildings (bridges, tunnels, irrigation and watering
systems and defensive installations).
Complex (natural-cultural) landscape objects are also preserved if they have
versatile scientific and educational value.
There are enough drained lands in Lithuania; therefore more attention should be
paid on maintenance, repair and reconstruction of drainage. Groves, single trees
and wetlands have to be preserved. For animal husbandry it is recommended to
produce coarse fodder according to traditional technologies giving preference to
haymaking. Usage of concentrated fodder should be reduced.
It is needed to expand grass plots in eroded lands and in karst region (Northern
Lithuania), to spread meadows, groves and wetlands more evenly in landscape and
ponds in existing rivulet network.
In order to preserve traditional Lithuanian agricultural landscape, shores of
rivulets and ditches and coastal strips have to be set aside, use of pesticides
reduced or replaced by natural materials (Fig. 8.6).
|
|
Fig. 8.6. Protective bush strip at
Nevezis riverside |
8.4. SOIL EROSION
Soil erosion - it is destructive activity of
wind or water streams affecting surface soil layer periodically.
8.14
Physical and juridical persons who use soil resources must:
| preserve and enhance soil
fertility;
| take measures in order to avoid
negative effect of soil erosion. |
|
Republic of Lithuania. Law on Change of
the Law on Land (draft), 1999.
Rainwater or snow melting waters that flow on soil surface in slope direction
cause water erosion. The steeper slope is, the higher speed and energy of the
flowing water become Harm
caused by water erosion varies very much: washout of fertile soil layer and
nutrients from slopes, destruction of crop fields in eroded slopes, destruction
of ditch slopes and roads, blocking of ditch bed with sediments, silting of
water bodies and pollution of waters.
The following water erosion types are defined:
- Sheet erosion (water flows in wide
streams washing out entire soil surface);
- Gully erosion (water accumulates and washes out small ditches, channels or
ravines).
Sheet erosion
For reducing of sheet erosion it
is recommended:
| to apply anti-erosive soil tillage;
| not to leave bare fallow;
| not to plough stubble in autumn;
| to avoid soil tillage with heavy machinery
that compacts soils;
| to exploit drainage systems properly;
| to apply anti-erosive crop rotations;
| to apply strip agriculture on slopes of
hills.
| |
| | | | | | |
Anti-erosive soil tillage.
Slopes of hilly lands have to be ploughed across slope turning soil upwards
(Fig. 8.7).
 Fig.
8.7. Slopes of hilly lands have to be ploughed across slope in order to reduce
erosion
Furrows that are formed across slope retain part of precipitation and reduce
runoff. Contour ploughing may also be applied, i.e. when ploughing is performed
not straight in one direction but exactly along horizontal line, turning soil
upwards or downwards of the slope.
These soil tillage types are more acceptable on rounded and not steep (under 5°)
hills. Very effective anti-erosive measure is soil tillage by heavy-duty
cultivator (chisel), but it may be applied only in not weedy soils.
Do not leave bare fallow; do not
plough stubble in autumn. This
measure is applied on fields where cereals grew. It may be used only in not
weedy soils.
Avoid soil tillage with heavy
machinery that compacts soil. Heavy
machinery increases soil compaction and reduces infiltration possibilities.
Plant germination and growth conditions become worse. Drainage is damaged.
Surface water runoff and soil erosion increase.
Apply anti-erosive crop rotation.
Sow winter crop (cover crop) and undercrop; distinctly expressed thalweg (longer
than 100 m) sow to perennial grasses.
Apply strip agriculture on slopes of
hills. Strip agriculture is a
combination of strips of cultivated land with strips of perennial grasses on
slopes keeping parallelism to the direction of main horizontal lines. It is
recommended to grow alfalfa, fescue and clover. Elements of strip agriculture
are recommended on slopes longer than 150 m (Table 8.1).
Table 8.1. Parameters of elements of row
agriculture
|
Slope
|
Sandy loam soils
|
Loam soils
|
|
in degrees
|
Width of grass strip m
|
Width of arable land strip m
|
Width of grass strip m
|
Width of arable land strip m
|
|
1-3
|
7
|
130
|
7
|
60
|
|
3-5
|
15
|
70
|
15
|
30
|
|
5-8
|
15
|
50
|
30
|
30
|
|
8-10
|
29
|
40
|
30
|
20
|
Gully (linear) erosion
Hydrotechnical measures are
recommended for reduction of linear erosion:
| choose allowed thalweg length according to
critical area of thalweg watershed;
| install concrete water gutters;
| install dykes that retain water. |
| |
Intensive erosion of thalweg in agricultural
area may be reduced by limiting of surface runoff that comes from certain area
of watershed and accumulates in thalweg. When accumulated flow exceeds critical
value, it has to be removed through drainage pipes. Gully water erosion is
dangerous for thalweg that has longitudinal slope of more than 1% and the area
of watershed is larger than given in table 8.2.
Table 8.2. Critical area of thalweg watershed (ha) on
arable land
|
Soil mechanical composition
|
Longitudinal inclination of thalweg in percent
|
|
2
|
3
|
5
|
7
|
10
|
| Sandy loam |
8.0
|
5.0
|
4.0
|
2.0
|
1.0
|
| Light loam |
9.0
|
6.0
|
4.0
|
3.0
|
1.5
|
| Medium loam |
11.0
|
8.0
|
5.0
|
4.0
|
3.0
|
| Clay loam and clay |
17.0
|
13.0
|
10.0
|
7.0
|
5.0
|
Thalweg that has watershed larger than critical value is divided into separate
parts so that the area of every part would not exceed the critical value.
Accumulated flow from every such part is removed through inlets of drainage. For
this purpose the thalweg is divided with a ground partition of 0.20-0.40 m
height, and before this dyke there are small pond and inlet arranged for
directing of surface water to drains. Slopes of the dyke are flat (ratio between
height and length of the slope is 1:3-1:8) and sown to perennial grasses (Fig.
8.8).
Install concrete water gutters.
They are used in such places when surface water coming from surrounding areas
accumulates and destroys slopes of ditches.
Install dykes that retain water.
Such dykes are arranged only if other measures can not stop enlarging of ravines
made by gully erosion. They are installed at the upper part of ravine. Their
purpose is to retain surface runoff and direct it to branch drains. The height
of dykes may be from 0.5 up to 2 m. Coefficients of slopes are 1.52.5.
Other hydrotechnical measures can also reduce gully erosion such as ditches that
direct water flow, construction of concrete riverbanks, small channels and dykes
to disperse water flow, cofferdams, rapids and dams. But every of these measures
is applied in certain cases and, besides, it has to be ecologically and
economically feasible.
 Fig.
8.8. Reduction of surface runoff through installation of dykes and directing of
surplus water to drainage: 1 ditch; 2 thalweg; 3 dykes; 4 small
ponds; 5 inlets for surplus water; 6 - drainage
Wind erosion is not intensive in Lithuania except for Curonian spit, coastal
regions and sandy soils of southeastern Lithuania. In middle Lithuania wind
erosion is active during snowless winter when soil is frozen and also in early
spring when soils become dry quickly. Minimal soil tillage is applied in order
to reduce effect of wind erosion. In autumn soil is not cultivated and in spring
crops are sown after cultivation of surface layer. This measure is not very
effective as weeds flourish in soil that was minimally cultivated and herbicides
must necessarily be used. Minimal soil tillage is applied only in well-improved
soils without weeds.
Other measure is protective vegetation strips (Fig. 8.9.).
 Fig.
8.9. Example of farm planting by vegetation: 1- main strip; 2 secondary
strip
Longer side of protective vegetation
strips has to be perpendicular to prevailing winds. Variety composition of
plants may be diverse (deciduous and coniferous trees and bushes). Perimeter of
protective vegetation strips around agricultural fields has to be at least
1.5-2.0 km per 100 ha of agricultural land. Recommended ration between the
length of protective vegetation strip and agricultural land in different regions
is the following: 15-40 m/ha in middle Lithuania; 40-60 m/ha in south-eastern
Lithuania; 60-100 m/ha in Auktaiθiai and emaiθiai highlands; 60-80 m/ha in
sea-shore plain.
Vegetation has to be planted first on plots that are not suitable for soil
cultivation in such places as in confluence of ditches, intersection of ditches
and roads, crossroads of field roads and by water bodies. Under conditions of
hilly relief the strongly eroded and drifting tops of hills and upper hillsides
are first planted by vegetation.
8.5. WETLANDS
Wetlands these are areas that are flooded
with water continually or periodically and that have specific hydrological
conditions, aquatic vegetation and soil. Wetlands are 'biological filters'
separating water bodies from adjacent areas. Water self-purifies while it goes
through such 'filter': pollutants sediment on thick grass vegetation and they do
not reach open water bodies.
Such areas are usually formed in flooded
or springy territories of uneven relief. In order to increase biological
diversity these areas could occupy from 10 to 15 % of agricultural area.
8.15
In flooded and springy areas it is forbidden:
· to
drain, plough (except for polders) and change otherwise state of flood
meadows and pastures and their grass composition;
· to
destroy vegetative cover of natural marshes mechanically;
· to
change hydrological regime of springs that do not dry up and their groups;
· to
drain and make agricultural lands or waters out of upland moors,
intermediate marshes and low-lying marshes that have area of more than 0.5
ha and depth of peat more than 1 m.
Special conditions on forest and land
use. LRG 1992.05.12, Resolution No. 343. V.
In order to preserve wetlands it is recommended:
| not to drain areas that are close to water
bodies;
| not to drain small swamps formed in zones
without flow or zones of divide thalweg (such places should be more
diversified with combination of trees and bushes);
| to avoid draining of hollows and springy
places not far from water bodies;
| to arrange sedimentation tanks for retention
of pollutants and eroded particles in already existing drainage ditches. |
| | |
Sedimentation tank it is a deepened and
widened section of ditch (Fig. 8.10). It can be arranged at every place of a
ditch. There water forms small pond, which becomes overgrown with aquatic
vegetation and retains suspended matter and fertiliser coming from fields. Such
pond suits for watering of animals and its water may be taken for watering of
fields too.
Fig. 8.10. Pond for retention of suspended matter
and fertiliser that come from fields: 1- drainage collector; 2,3,4- groups of
bushes and various trees
|
